A PFO is best thought of as a communication at the level of the atrial septum between the left heart and the right heart.

It is found in 25-30% of a normal healthy population and usually does not cause any symptoms, impact on the quality of life or lifespan.

Many people refer to it as a ‘hole in the heart’ although strictly speaking, a PFO is more like a flap or a partially open door rather than a gaping hole.

Most patients with PFO are asymptomatic. However, there are 4 situations in which a PFO may be important and partially be responsible for harm.